JavaScript by Example: JavaScript Core Objects. Pt. 1

Math object properties.

Property

Value

Description

Math.E

2.718281828459045091

Euler's constant, the base of natural logarithms

Math.LN2

0.6931471805599452862

Natural log of 2

Math.LN10

2.302585092994045901

Natural log of 10

Math.LOG2E

1.442695040888963387

Log base-2 of E

Math.Log10E

0.4342944819032518167

Log base-10 of E

Math.PI

3.14592653589793116

Pi, ratio of the circumference of a circle to its diameter

Math.SQRT1_2

0.7071067811865475727

1 divided by the quare root of 2

Math.SQRT2

1.414213562373985145

Square root of 2

Math object methods.

Method

Functionality

Math.abs(Number)

Returns the absolute (unsigned) value of Number

Math.acos(Number)

Arc cosine of Number, returns result in radians

Math.asin(Number)

Arc sine of Number, returns results in radians

Math.atan(Number)

Arctangent of Number, returns results in radians

Math.atan2(y,x)

Arctangent of y/x; returns arctangent of the quotient of its arguments

Math.ceil(Number)

Rounds Number up to the next closest integer

Math.cos(Number)

Returns the cosign of Number in radians

Math.exp(x)*

Euler's constant to some power (see footnote)

Math.floor(Number)

Rounds Number down to the next closest integer

Math.log(Number)

Returns the natural logarithm of Number (base E)

Math.max(Number1, Number2)

Returns larger value of Number1 and Number2

Math.min(Number1, Number2)

Returns smaller value of Number1 and Number2

Math.pow(x, y)

Returns the value of x to the power of y(xy), where x is the base and y is the exponent

Math.random()

Generates pseudorandom number between 0.0 and 1.0

Math.round(Number)

Rounds Number to the closest integer

Math.sin(Number)

Arc sine of Number in radians

Math.sqrt(Number)

Square root of Number

Math.tan(Number)

Tangent of Number in radians

Math.toString(Number)

Converts Number to string

* Returns the value of Ex where E is Euler's constant and x is the argument passed to it. Euler's constant is approximately 2.7183.


<html> <head><title>The Math Object</title></head> <body> <h2>Math object Methods--sqrt(),pow()<br> Math object Property--PI</h2> <P> <script language="JavaScript"> 1 var num=16; document.write("<h3>The square root of " +num+ " is "); 2 document.write(Math.sqrt(num),".<br>"); document.write("PI is "); 3 document.write(Math.PI); document.write(".<br>"+num+" raised to the 3rd power is " ); 4 document.write(Math.pow(num,3)); document.write(".</h3></font>"); </script> </body></html>

<html>

<head><title>The Math Object</title></head>

<body>

<h2>Math object Methods--sqrt(),pow()<br>

Math object Property--PI</h2>

<P>

1 var num=16;

document.write("<h3>The square root of " +num+ " is ");

2 document.write(Math.sqrt(num),".<br>");

document.write("PI is ");

3 document.write(Math.PI);

document.write(".<br>"+num+" raised to the 3rd power is " );

4 document.write(Math.pow(num,3));

document.write(".</h3></font>");

</script>

</body></html>

Rounding up and down.
Number	ceil()	floor()	round()
2.55	3	2	3
2.30	3	2	2
-2.5	-2	-3	-2
-2.3	-2	-3	-2

Rounding up and down.

Number

ceil()

floor()

round()

2.55

2.30

-2.5

-2

-3

-2

-2.3

-2

-3

-2


<html> <head><title>The Math Object</title></head> <body> <h2>Rounding Numbers</h2> <p> <h3> <script language="JavaScript"> 1 var num=16.3; document.write("<I>The number being manipulated is: ", num, "</I><br><br>"); 2 document.write("The <I>Math.floor</I> method rounds down: " + Math.floor(num) + "<br>"); 3 document.write("The <I>Math.ceil</I> method rounds up: " + Math.ceil(num) +"<br>"); 4 document.write("The <I>Math.round</I> method rounds to\ the nearest integer: " + Math.round(num) + "<br>"); </script> </h3> </body> </html>

<html>

<head><title>The Math Object</title></head>

<body>

<h2>Rounding Numbers</h2>

<p>

<h3>

1 var num=16.3;

document.write("<I>The number being manipulated is: ", num,

"</I><br><br>");

2 document.write("The <I>Math.floor</I> method rounds down: " +

Math.floor(num) + "<br>");

3 document.write("The <I>Math.ceil</I> method rounds up: " +

Math.ceil(num) +"<br>");

4 document.write("The <I>Math.round</I> method rounds to\

the nearest integer: " + Math.round(num) + "<br>");

</script>

</h3>

</body>

</html>


<html><head><title>Random Numbers</title> <font size="+1"> <script language="JavaScript"> 1 var n = 10; 2 for(i=0; i < 10;i++){ // Generate random numbers between 0 and 10 3 document.write(Math.floor(Math.random()* (n + 1)) + "<br>"); } </script> </head> <body></body> </html>

<html><head><title>Random Numbers</title>

1 var n = 10;

2 for(i=0; i < 10;i++){

// Generate random numbers between 0 and 10

3 document.write(Math.floor(Math.random()* (n + 1)) +

"<br>");

}

</script>

</head>

</html>


The variable n is assigned an initial value of 10. This value will be the outside range of numbers randomly produced.
The for loop is entered and will cause the body of the block to be executed 10 times, thus producing 10 random numbers between 0 and 10. The formula produces a random number between 0 and some number, n, using the Math object's random method. The output is shown in Figure 9.19.

The variable n is assigned an initial value of 10. This value will be the outside range of numbers randomly produced.

The for loop is entered and will cause the body of the block to be executed 10 times, thus producing 10 random numbers between 0 and 10.
The formula produces a random number between 0 and some number, n, using the Math object's random method. The output is shown in Figure 9.19.